MANCHESTER -- Portland catcher Blake Swihart and the rest of the Sea Dogs and Fisher Cats who played in Wednesday night’s Eastern League All-Star Game were late arriving in Manchester on Thursday, forcing their managers to rewrite their starting lineups.

Swihart is expected to be behind the plate for Friday night’s game against New Hampshire, but how many more times Portland manager Billy McMillon gets to write his name on the lineup card is an open question.

When the Red Sox designated A.J. Pierzynski for assignment and promoted Christian Vazquez from Triple-A Pawtucket to Boston just before the All-Star break, promoting Swihart from Double-A seemed like the logical next move in a series of corresponding transactions. The presence of Vazquez and Swihart in the upper levels of the Sox’ farm system, after all, were Reasons 1 and 1A why they let Jarrod Saltalamacchia walk and signed Pierzynski to a short-term contract.

And, like Vazquez, Swihart had done nothing to diminish the organization’s faith in him.

A 22-year-old switch-hitter who had never played above the Single-A level before this season, Swihart entered the break hitting .296 with 20 home runs, 48 RBIs, an on-base percentage of .351 and an OPS of .836. His defensive value was evidenced by Portland’s league-best 3.65 ERA and by the percentage of runners he had gunned down trying to steal: 53 (26 of 49).

But instead of promoting Swihart, who is considered to have even a higher ceiling than the very promising Vazquez, Boston promoted his backup, 29-year-old Matt Spring, who appears destined to be a career minor-leaguer.

McMillon and Portland hitting coach Rich Gedman, the former Red Sox catcher, could only theorize as to why Swihart is still here. Both praised his performance at and behind the plate, his overall athleticism, his intelligence, his work ethic.

“And,” added Gedman, “he’s a great teammate.”

So why was Swihart hustling onto the field during Portland batting practice Thursday while Dan Butler was preparing to start for the PawSox?

“Dan Butler is on the (Red Sox) 40-man roster,” McMillon noted. “It’s not like they don’t have a catcher up there in Pawtucket.”

While Butler isn’t rated nearly as strong a prospect as Vazquez or Swihart, he is considered a potential major-league backup and therefore a possible secondary chip in a pre-trading-deadline deal. Some added exposure in Pawtucket with Swihart still in Portland can’t hurt.

Moreover, said McMillon, “Sometimes it’s not a bad thing to have a full year at a level. Better that than to rush a player.”

Gedman, making it clear he was only speculating, offered another possible reason why the Red Sox have delayed Swihart’s promotion.

“Maybe they want to keep him here until Henry Owens moves up,” he said. “He’s a part of a class here, if you will, that’s developed some confidence together.”

Swihart and Owens, the Red Sox’ top pitching prospect, have risen through the ranks together, and the 6-foot, 6-inch left-hander shares credit for his 12-3 record and 2.21 ERA with his batterymate.

“He’s always had a really strong arm, and he’s always been very athletic and able to block balls and frame pitches,” Owens said. “Now his instincts for the game have surpassed the level he’s played at.”

For now, Swihart’s level remains Double-A. That promotion’s coming, but like his arrival in Manchester on Thursday, it may be delayed just a bit.

Vin Sylvia is a New Hampshire Union Leader deputy managing editor. Email him at vsylvia@unionleader.com. Follow him on Twitter @vinsylvia.